1. Field of the Invention
The present invention relates to a light guide plate and back light module having the same, and more particularly to a light guide plate having a plurality of microreliefs disposed on the reflecting surface thereof.
2. Description of the Related Art
FIG. 1 shows a schematic view of a conventional back light module. The back light module 1 comprises a light source 11, a reflector 12, a light guide plate 13 and films 16. The films 16 comprise a diffusion film, an enhanced brightness film and so on. The light source 11, for example, a LED light bar or CCFL, is used to provide a light beam. The reflector 12 is disposed below the light guide plate 13, and is used to reflect part of the light beam back to the light guide plate 13.
The light guide plate 13 is used to receive and mix the light beam from the light source 11. The light guide plate 13 includes a light guide plate body 14 and an ink 15. The light guide plate body 14 has a reflecting surface 141, a light-emitting surface 142 and a light incident surface 143. The reflecting surface 141 is opposite the light-emitting surface 142, and the light incident surface 143 is adjacent to the reflecting surface 141 and the light-emitting surface 142. The light source 11 faces the light incident surface 143, so that the light beam enters the light guide plate body 14 through the light incident surface 143 and then is transmitted to the films 16 through the light-emitting surface 142. The material of the light guide plate body 14 is transparent polymer, for example, polymethyl methacrylate (PMMA) or polycarbonate (PC).
The ink 15 is printed on the reflecting surface 141 of the light guide plate body 14 to form a pattern, so as to reflect the light beam back to the interior of the light guide plate body 14. The ink 15 includes a base resin, a filler, a solvent, an additive and a curing agent. The material of the base resin is epoxy resin, polyester resin, acrylic resin, polyvinyl resin, polyamide resin or polyurethane resin. The material of the filler and the additive are inorganic, for example, silica (SiO2).
The disadvantage of the conventional back light module 1 is described as follows. As shown in FIG. 2, the light beam reflected by the ink 15 will scatter with large angle, such as the light beam 18. The light beam 18 will cause total internal reflection on the light-emitting surface 142, and then propagates continuously in the interior of the light guide plate body 14. As a result, only part of the light beam is transmitted out of the light guide plate body 14, thus the light extraction efficiency is limited.
Therefore, it is necessary to provide a light guide plate and back light module having the same to solve the above problems.